1. Field of the Invention
The present invention relates to a non-metallic material for a gear, and more particularly to a carbon-filament reinforced material of laminated structure to be worked into a gear.
2. Description of the Prior Art
With a view to reducing the noises, a gear made of plastics such as a polyester resin has been widely used as a light-load gear. However, the plastic gear is limited to the light load use because no plastic material has such a strength as can stand a heavy load. The conventional plastic material for the gear is made of a thermoplastic resin so that it has poor heat resistivity (more specifically, it has been experimentally revealed to be subject to deformation at a temperature as low as about 100.degree. C.). Thus, the conventional material has failed to find its suitable application not only in case the gear itself liberates heat due to friction but also in case the gear is used at a high temperature together with a dryer or heater. On the other hand, a gear made of fiber-glass reinforced plastics has also been developed, but it cannot enjoy sufficient fatigue strength.
With this in mind, there has been proposed the use of carbon fibers which are excellent in both the fatigue strength and the heat resistivity. In this instance, the carbon filament fabric must be of plain weave type, that is, woven fabrics in which the warps and wefts are composed of carbon filaments of several hundreds and thousands bundled into strands by means of a binding agent. Without any treatment, therefore, the binding agent will not be admixed sufficiently with a binding agent which may be made of a plastic material for adhering the plain weave fabrics together. Even if, moreover, those fabrics are laminated under pressure, the eyes or voids of the stitches left between the adjacent warps and wefts will hardly be filled up with the binding agent, thus causing the inter-layer separation.
In the case of the use of such carbon-filament reinforced fabrics, there arises another problem, in which the high speed hob of wide use for cutting operations cannot be employed because the hob itself is cut by the work. In this case, moreover, even a super hard hob cannot be expected to have excellent workability but is so remarkably worn and damaged as to deteriorate the economy. Still moreover, the working degree cannot exceed the rough ground finish. On the other hand, there is left unsolved another problem how to use the fabrics, in which carbon filaments are arranged with directivity, as a material for a gear which is intrinsically incompatible with the directivity.